The drive to reduce the minimum feature sizes of microelectronic devices to meet the demand for faster, lower power microprocessors and digital circuits has introduced new materials and processes into device manufacturing. These new materials include low dielectric constant (low-k) materials and ultra-low-k (ULK) materials that can provide several advantages relative to the traditional silicon dioxide dielectric materials. For example, the use of low-k fluoro-carbon materials to separate conductive lines in semiconductor devices reduces the RC time constant by reducing the capacitance, which in turn, increases the speed of the device.
Fluoro-carbon films have attracted a great deal of interest not only as material for interlayer dielectrics in ultra-large scale integrated (ULSI) circuits, but also for electrical insulation in electrical equipment, because of their low dielectric constant, high-dielectric strength, and chemical inertness. Although low-k fluoro-carbon materials have a number of advantageous properties, they tend to be less chemically robust than more traditional oxide and nitride dielectric layers and they can suffer from problems that limit their use in typical semiconductor processes. These problems include outgassing (e.g., fluorine outdiffusion) and undesirable chemical reactions during processing, and poor adhesion to other materials in the semiconductor device.